# C++14 feature support detection

include(CheckCXXCompilerFlag)

function(fmt_check_cxx_compiler_flag flag result)
	if(NOT MSVC)
		check_cxx_compiler_flag("${flag}" ${result})
	endif()
endfunction()

if(NOT CMAKE_CXX_STANDARD)
	set(CMAKE_CXX_STANDARD 11)
endif()

message(STATUS "CXX_STANDARD: ${CMAKE_CXX_STANDARD}")

if(CMAKE_CXX_STANDARD EQUAL 20)
	fmt_check_cxx_compiler_flag(-std=c++20 has_std_20_flag)
	fmt_check_cxx_compiler_flag(-std=c++2a has_std_2a_flag)

	if(has_std_20_flag)
		set(CXX_STANDARD_FLAG -std=c++20)
	elseif(has_std_2a_flag)
		set(CXX_STANDARD_FLAG -std=c++2a)
	endif()

elseif(CMAKE_CXX_STANDARD EQUAL 17)
	fmt_check_cxx_compiler_flag(-std=c++17 has_std_17_flag)
	fmt_check_cxx_compiler_flag(-std=c++1z has_std_1z_flag)

	if(has_std_17_flag)
		set(CXX_STANDARD_FLAG -std=c++17)
	elseif(has_std_1z_flag)
		set(CXX_STANDARD_FLAG -std=c++1z)
	endif()

elseif(CMAKE_CXX_STANDARD EQUAL 14)
	fmt_check_cxx_compiler_flag(-std=c++14 has_std_14_flag)
	fmt_check_cxx_compiler_flag(-std=c++1y has_std_1y_flag)

	if(has_std_14_flag)
		set(CXX_STANDARD_FLAG -std=c++14)
	elseif(has_std_1y_flag)
		set(CXX_STANDARD_FLAG -std=c++1y)
	endif()

elseif(CMAKE_CXX_STANDARD EQUAL 11)
	fmt_check_cxx_compiler_flag(-std=c++11 has_std_11_flag)
	fmt_check_cxx_compiler_flag(-std=c++0x has_std_0x_flag)

	if(has_std_11_flag)
		set(CXX_STANDARD_FLAG -std=c++11)
	elseif(has_std_0x_flag)
		set(CXX_STANDARD_FLAG -std=c++0x)
	endif()
endif()
